Lost Torque on 2006 Mazda 3
 

I have a 2006 Mazda 3, manual 5 spd, with 2.3L engine. Has about 45,000 miles on it.

Clutch shifts smooth in all gears. Clutch pedal is getting soft and quite close to floor.

Recently, I lost a lot of torque. Just happened overnight. Now, the engine drives too "smooth", like grandma's car. Can't even burn rubber in first gear on dry road, no matter how hard I try. No torque.

It is like this in every gear. So higher revs than usual, with less acceleration. I know this is typically a worn clutch, but given that it happened overnight, could it be something else?

Clutch fluid is up at proper level, and never any clutch burning smell. No slipping or chattering of clutch either.

Could it be torque converter clutch, vacuum leak, etc?